1. Field of the Invention
The present invention relates to a method and an apparatus for detecting whether a catheter is the cause of sepsis in a patient without unnecessarily removing the catheter from a patient.
2. Art Background
For a number of years, central venous catheters have been used widely in medicine in the critical care area. These catheters are commonly used to perform a number of different, but equally important functions, among which include
(a) measuring central pressure; PA1 (b) monitoring and modifying fluid volume; PA1 (c) administering one or more therapeutic substances simultaneously; PA1 (d) providing a secure site of intravenous ("IV") access; and PA1 (e) conducting blood therapy.
Furthermore, these catheters also are used in long-term treatment, such as chemotherapy and parenteral nutrition (so called "Hickman catheter").
Venous catheters are inserted into a patient "peripherally" through a cephalic or basilic vein, or "centrally" through the internal jugular, external jugular, subclavian or saphenous vein. Determining which type of insertion is based on many factors; however, any type insertions typically causes at least some discomfort and pain to the patient, and requires a reasonable amount of skill, and each insertion is subject to certain inherent risks and costs. In addition to venous catheters, there are also peritoneal catheters, urethral catheters, such as the Foley catheter, and arterial catheters in the prior art.
According to various studies, approximately 4-15% of the venous catheters are the cause of secondary infections. On the average, in about 60% of the cases in which there is sepsis, the catheter cannot be ruled out as the cause, and the catheter is removed to make a determination if it is the cause, as described in more detail below. Even though only a small percentage of catheters are the cause of such infections, hospitals are required to continuously monitor catheters for possible catheter sepsis (i.e., infections within an indwelling line of a catheter) which may cause complications in a patient's treatment leading to sickness or even death.
The current diagnostic techniques used to detect catheter sepsis are problematic. If a physician or nurse suspects that an infection is being caused by the catheter, the suspect catheter is removed and replaced with a new catheter. The tip of the suspect catheter is removed under sterile conditions and sent to the lab for contamination testing. If the catheter is found to be infected, physicians can provide treatment in accordance with standard medical procedures for such infection.
This procedure, called a "tip culture ", offers a number of disadvantages. The primary disadvantage is that since only a small percentage of the catheters become infectious, patients quite often experience additional pain and discomfort due to the unnecessary removal of the catheters. Also, the insertion of a new catheter can be associated with additional risks of infection, such as bleeding, pneumothorax, and infection. Moreover, the removal of non-infected catheters contributes to rising medical costs.
One prior art method of identifying and locating dental microorganisms is disclosed in U.S. Pat. No. 4,368,272 comprising a flexible strip of material with a sterile velvet material that is contacted with the teeth and then cultured.
Another prior art test method and apparatus for testing whether there is any infectious material in the contents in syringe is described in U.S. Pat. No. 4,397,945, which teaches the use of a sampling device for sampling a portion of the contents of the syringe.
Also in the prior art are cytology brushes which are used to collect cells for analysis. It is not believed that such a brush has heretofore been used for a sampling system for microbial infection.
Another prior art method previously developed by the present inventor is described in a publication entitled Markus, Stan and Buday, Stephen, "Culturing Indwelling Central Venous Catheters In Situ," Infections in Surgery, May 1989, pp. 157-160, and a review article Beam, Thomas, "Vascular Access, Catheters and Infections," Infections in Surgery, May 1989, pp. 156; 161-162. The Markus, et al. article teaches a method and apparatus for assessing whether central venous catheters is causing catheter sepsis in situ. The apparatus comprises a thin wire with either a stop or separate handle on or near one end, and a brush at the other end. The apparatus is specifically designed so that it cannot protrude through the end of the catheter. The brush is designed to fit the exact length of the catheter in situ, and a metal stopper ensures that the brush does not go beyond the catheter tip and does not damage the vein wall during sampling. (See FIG. 2 at p. 158).
Thus, there is a need for a better method and apparatus for determining the existence of infections being caused by an indwelling catheter, which method and apparatus do not have the drawbacks of the prior art.